Fundamental Research On Vetrification Of Simulated Radioactive Waste With Pu

It will be a terrifying disaster to the human being, if radioactive waste leak out and enter into the biosphere. All radioactive waste shall be transformed into a stable, firm and inert solid form before final disposition of the waste. Considering the process and the properties of the waste form, Vetrification is the most mature, reliable and safe approach to immobilizing radioactive waste. The fundamental research on Vetrification of radioactive waste enriched with Pu was carried out.On the basis of fully investigation into the achievement on Vetrification of High Level Waste (HLW) and disposal of excess Pu carried out abroad, for radioactive waste enriched with Pu, Ce was introduced as the simulant of Pu, and borosilicate glass was adopted as the glass matrix for immobilization of the waste.Thorough orthogonal design and water tolerance test, several glasses with high water resistance and low melting temperature were obtained, amount which P19-5 glass has the best water resistance with high content of simulant. The composition of P19-5 glass is: SiO₂ 46.5wt.%, B₂O₃ 18.9wt.%, Al₂O₃ 6.31wt.%, Na₂O 7.58wt.%, Li₂O 2.53wt.%, K₂O 2.53wt.%, CaO 3.79wt.%, ZnO 2.53wt.%, CeO₂ 4.65wt.%, Gd₂O₃ 4.65wt.%.The leaching behavior of P19-5 glass at different temperatures was investigated thorough long-term leaching test, and the test duration was not more than 148days. It shows that the glass has a good long-term durability with low leaching rate: the initial 70aching rate at 90℃is about 0.3 g/ m²Â·d; the leaching rates at 25-70℃are comparative, and about an order lower than that at 90℃; the leaching rate of Ce is about 3-4 orders lower than that of glass matrix, most of Ce is reserved in the surface layer by in situ reconstruction; after corrosion, a gel layer was formed on the surface of the glass, and the gel layer play a protect role leading to a low leaching rate in the late stage of the test; compared with other HLW glasses, P19-5 glass has a much lower leaching rate and better water resistance. Leaching tests carried out in different conditions show that a dense gel layer can be formed in short duration (28days) and result in the drop of leaching rate by about 2 orders. The addition of various ions in the leachant has different influence on the leaching rate and the formation of the gel layer.The devetrification of the glass after heat treatment was determined by XRD and SEM-EDS, and it shows P19-5 glass has no change after heated at 400℃for 10 days, while it is devitrified slowly at 500℃,...